Yamaha M70 Amp : Is this true ?...Warning of mylar capacitor being fire hazard

why dont you contact Yamaha and ask them ??

Look up the issue with the A-560, A-760 and the A-960 integrated amplifiers.

They have a power supply ’trick’ they borrowed from Bob Carver, and they were forced to remove the power supply tweak circuit, when he sued them for infringement. This is the reason they (Yamaha) made the A-560II, A-760II, and the A-960II models. They removed the Power supply modification and actually made a different amp. The originals are better, although not specifically for the Bob Carver originated power supply trick/tweak.

those three original models have the potential for the same capacitor failure in this power supply circuit.

Your M-70 is from the same time period of design and product issue and from looking at images of the innards of the M-70, it appears to have the same thing going on in it. The capacitor involved is at the back of the amp, behind the transformer, near that tall heat-sink, near where the power comes in.

That capacitor DOES need to come out of there and a newer, high quality one needs to be installed. Otherwise it can "let go" and when it does, it is nearly a fire hazard. They do tend to get to being a bit of a ’flame out’.

At such a time, you’ll be looking at something that looks like a fully blown repair job instead of a simple capacitor swap. Meaning, it is potentially messy if it lets go. Not literally and not in my recollection has it ever been a huge mess... but it is still a potential mess waiting to happen.

Do the swap, sidestep the eventuality. I do mean eventuality. It WILL let go. It is only a matter of time and that time is tied to how much the amp has been used, in hours of on time, combined with the noise level on your particular AC power lines.

http://www.diyaudio.com/forums/solid-state/92796-yamaha-760-quot-power-supply-quot-help.html

Well, this is interesting. The "trick" was really quite advanced voltage tracking power supply.

This isn't just a mod, but an entirely different power supply.

Also interesting, is that the Yamaha EEEngine and nuForce seem to use variants of this idea today.